Department of Medicine, University of California, San Francisco, San Francisco, CA, 94110, USA.
Center for Vulnerable Populations, Zuckerberg San Francisco General Hospital and Trauma Center, University of California, San Francisco, San Francisco, CA, USA.
BMC Med. 2021 May 7;19(1):116. doi: 10.1186/s12916-021-01965-y.
COVID-19 outbreaks have occurred in homeless shelters across the US, highlighting an urgent need to identify the most effective infection control strategy to prevent future outbreaks.
We developed a microsimulation model of SARS-CoV-2 transmission in a homeless shelter and calibrated it to data from cross-sectional polymerase chain reaction (PCR) surveys conducted during COVID-19 outbreaks in five homeless shelters in three US cities from March 28 to April 10, 2020. We estimated the probability of averting a COVID-19 outbreak when an exposed individual is introduced into a representative homeless shelter of 250 residents and 50 staff over 30 days under different infection control strategies, including daily symptom-based screening, twice-weekly PCR testing, and universal mask wearing.
The proportion of PCR-positive residents and staff at the shelters with observed outbreaks ranged from 2.6 to 51.6%, which translated to the basic reproduction number (R) estimates of 2.9-6.2. With moderate community incidence (~ 30 confirmed cases/1,000,000 people/day), the estimated probabilities of averting an outbreak in a low-risk (R = 1.5), moderate-risk (R = 2.9), and high-risk (R = 6.2) shelter were respectively 0.35, 0.13, and 0.04 for daily symptom-based screening; 0.53, 0.20, and 0.09 for twice-weekly PCR testing; 0.62, 0.27, and 0.08 for universal masking; and 0.74, 0.42, and 0.19 for these strategies in combination. The probability of averting an outbreak diminished with higher transmissibility (R) within the simulated shelter and increasing incidence in the local community.
In high-risk homeless shelter environments and locations with high community incidence of COVID-19, even intensive infection control strategies (incorporating daily symptom screening, frequent PCR testing, and universal mask wearing) are unlikely to prevent outbreaks, suggesting a need for non-congregate housing arrangements for people experiencing homelessness. In lower-risk environments, combined interventions should be employed to reduce outbreak risk.
美国各地的无家可归者收容所发生了 COVID-19 疫情爆发，这凸显出迫切需要确定最有效的感染控制策略，以防止未来的疫情爆发。
我们开发了一种 SARS-CoV-2 在无家可归者收容所传播的微观模拟模型，并使用 2020 年 3 月 28 日至 4 月 10 日期间在美国三个城市的五个无家可归者收容所进行的横断面聚合酶链反应（PCR）调查数据对其进行了校准。我们估计了在不同感染控制策略下，当一个暴露个体在 30 天内引入一个有 250 名居民和 50 名工作人员的代表性无家可归者收容所时，避免 COVID-19 疫情爆发的概率，这些策略包括基于每日症状的筛查、每两周进行一次 PCR 检测和普遍戴口罩。
有疫情爆发的收容所中居民和工作人员的 PCR 阳性比例范围为 2.6%至 51.6%，这转化为基本繁殖数（R）估计值为 2.9-6.2。在社区发病率适中（~30 例确诊病例/每 100 万人/天）的情况下，在低风险（R = 1.5）、中度风险（R = 2.9）和高风险（R = 6.2）收容所中，避免疫情爆发的估计概率分别为每日基于症状的筛查为 0.35、0.13 和 0.04；每两周进行一次 PCR 检测为 0.53、0.20 和 0.09；普遍戴口罩为 0.62、0.27 和 0.08；这些策略联合使用时为 0.74、0.42 和 0.19。随着模拟收容所内传播性（R）的增加和当地社区发病率的增加，避免疫情爆发的概率降低。
在高风险的无家可归者收容所环境中和 COVID-19 社区发病率高的地方，即使采用强化感染控制策略（包括每日症状筛查、频繁的 PCR 检测和普遍戴口罩）也不太可能预防疫情爆发，这表明需要为无家可归者提供非群居住房安排。在风险较低的环境中，应采用联合干预措施来降低疫情爆发的风险。
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